Cows and Bulls

Cows and Bulls or Bulls and Cows is an old code-braking mind game similar to the board game Mastermind.
The game is played using a four digit number.
Your goal is to guess a random secret number that doesn't contain any duplicates.
For each guess you can receive a hint like 'bull' or 'cow'.
Example:
Secret number: 4271
Your guess: 1234
Answer: 1 bull and 2 cows. (The bull is "2", the cows are "4" and "1".)
Try to guess the secret number using as little as possible turns.
Good Luck!